Sunfish, thanks a lot for the insightful reply.
Yes, the effects of high turbine inlet temperature are very real, measurable and computable, not only increasing cost, but also statistically reducing reliability. Big carriers dealing with tens of thousands of flights every year have to take that into account.
Originally Posted by Sunfish
Despite the internal cooling, the gas stream gradually erodes the blades and vanes, and the rate of erosion is a direct function of temperature and time. The hotter they are, the longer they are, the shorter their life before they degrade to the point where they must be exchanged. I can't find images on the net of what they look like before they are replaced, but I can say they look something like a sort of melted turbine blade shaped icecream.
Here's an interesting
article about turbine blade coating, that contains some photos that dramatically show the erosion (and also, how advanced coatings reduce that erosion).
In some of the blades you can see little holes, which are the outlets for the cooling air mentioned. It is pumped into the blades from the root, and blown over their surface to keep them from melting.
Bernd